The ever increasing production of waste polymeric materials as by-products of industrial processes, and the like, has created a well recognized need for the disposal of such materials preferably providing some economical commercial use for them.
The heat content of most polymeric waste materials makes them potentially useful as fuels. However, many higher and intermediate molecular weight polymeric materials are semi-solids at room temperature, e.g. atactic polypropylene, which are difficult to feed and atomize and hence not suitable for direct burning in conventional systems. Various methods of thermally decomposing these polymeric waste materials into lower molecular weight fragments that are easy to handle and have economic value such as fuel oils and raw materials for industry are known in the art, for example see: U.S. Pat. Nos. 3,829,558, 3,832,151 or 4,151,216. A major problem with the known processes is accumulation of by-products, in particular, carbonaceous materials, on the heat transfer surfaces of the thermal reactors. Build-up of these materials on the heat transfer surfaces limits their efficiency and requires batch type operation or periodic shut downs for cleaning. The non-uniform heating characteristics of conventional furnaces contributes to this problem by creating hot spots on heat transfer surfaces along the path of waste materials to be thermally decomposed which promotes the accumulation of carbonaceous deposits. None of the techniques proposed in the prior art for dealing with this problem such as lower reaction temperatures, dispersal of accumulated carbon, and discharge of carbon rich fractions of the reactor material have sufficiently eliminated this problem to create a commercially viable continuous process.